It should contain more information like:
I've tested the variables below in a nodeDeleted event and no one resolved a value. I guess the values are not known any more because ONMS deletes first and then creates the event.
Here an example how the new content could look like:
Node %nodelabel% was deleted
%nodelabel% in location %location% was deleted from requisition %foreignsource%.
This can have multiple reasons.
OpenNMS default config will delete any node that is down for seven consecutive days
It was removed from the corresponding requisition /opennms/admin/ng-requisitions/index.jsp#/requisitions/%foreignsource%. This can be done manually using the web ui or using provisiond import schedules.
It was manually deleted using the "delete node" /opennms/admin/deleteNodes menu.
It was removed using the API
Please verify if the deletion was planned.